The present invention relates to packaging machines for containers such as cartons for containing milk, and more particularly to packaging machines including a bottom breaker.
As disclosed, for example, in JP-A 58-215338, packaging machines of the type mentioned are already known for use with tubular containers of square to rectangular cross section. The containers each have a bottom forming portion comprising first to fourth bottom panels continuous with one another, the first bottom panel having a pair of cuts formed in the center of the outer end thereof to provide a fold forming portion between these cuts for preventing a liquid from permeating the end. The packaging machine comprises a rotor having radial mandrels and intermittently drivable so as to stop each of the mandrels at a process station, the container being fitted around the mandrel with the first and third bottom panels facing toward a direction orthogonal to the direction of movement of the mandrel, and a bottom breaker for prefolding the bottom forming portion of the container as fitted around the mandrel stopped at the station so as to render the bottom forming portion foldable flat. The bottom breaker has a pair of first prefolding members which are free to open and close, and a pair of second prefolding members which are free to open and close. The second and fourth bottom panels are folded first by the movement of the first prefolding members from an open position toward a closed position, and the first and third bottom panels are folded subsequently by the movement of the second prefolding members from an open position toward a closed position. The bottom breaker further has a third prefolding member for prefolding the fold forming portion by bending this portion outward along the base part thereof. The third prefolding member is movable on the axis of the mandrel as stopped at the process station toward and away from the bottom forming portion fitted around the mandrel. When moving toward the bottom forming portion, the third prefolding member bends the fold forming portion by coming into striking contact therewith. The third prefolding member is operated by the same actuator as used for operating the first and second prefolding members.
With the conventional machine, the fold forming portion is bent by the straight movement of the third prefolding member, can not therefore be prefolded or bent effectively and is likely to restore itself from the bent form to the original state owing to the property of the container material to spring back. A faulty bottom portion will then be formed.
Further if the third prefolding member is to be reciprocatingly moved straight, a relatively great cycle time is required which is not suited to the high-speed operation of the packaging machine.
Further because a single actuator is used in common for the first to third prefolding members, it is impossible to bring the third prefolding member only out of operation. This means that containers having no fold forming portion can not be produced by the machine.
An object of the present invention is to overcome the above problems and to provide a packaging machine by which the fold forming portion can be bent to a full extent and which is adapted for a high-speed operation, the machine further being adapted to discontinue the fold forming portion bending operation only.
The present invention provides a packaging machine for tubular containers of square to rectangular cross section, each of the containers having a bottom forming portion comprising first to fourth bottom panels continuous with one another, the first bottom panel being formed with a fold forming portion in a center of an outer end thereof for preventing a liquid from permeating the end, the packaging machine comprising: a movable body having mandrels and intermittently drivable so as to stop each of the mandrels at a process station, the container being fitted around the mandrel with the first and third bottom panels facing toward a direction orthogonal to the direction of movement of the mandrel, and a bottom breaker for prefolding the bottom forming portion of the container as fitted around the mandrel stopped at the station so as to render the bottom forming portion foldable flat, the bottom breaker having a first prefolding member and a second prefolding member, the first prefolding member being operable to fold the second and fourth bottom panels initially, the second prefolding member being operable to fold the first and third bottom panels subsequently, the bottom breaker further having a third prefolding member for prefolding the fold forming portion by bending the fold forming portion outward along a base part thereof, the third prefolding member being pivotally movable from a nonoperative position to a second operative position via a first operative position, the fold forming portion being movable with the first bottom panel by the operation of the second prefolding member so as to be brought into contact with the third prefolding member and thereby bent outward while or after the third prefolding member is pivotally moved from the nonoperative position toward the first operative position, the third prefolding member being pivotally movable from the first operative position toward the second operative position after the operation of the second prefolding member to thereby bend the fold forming portion through an increased angle.
With the packaging machine of the present invention, the third prefolding member is pivotally movable from a nonoperative position to a second operative position via a first operative position. The fold forming portion is moved with the first bottom panel by the operation of the second prefolding member so as to be brought into contact with the third prefolding member and thereby bent outward while the third prefolding member is pivotally moved from the nonoperative position toward the first operative position. The third prefolding member is pivotally moved from the first operative position toward the second operative position after the operation of the second prefolding member to thereby bend the fold forming portion through an increased angle. Accordingly, the fold forming portion is bent by two steps, i.e., by the first step of bending this portion utilizing the movement of the first bottom panel by the operation of the second prefolding member, and the second step of bending the portion by the pivotal movement of the third prefolding member. Consequently, the fold forming portion can be bent to a full extent.
Further the movement of the third prefolding member is pivotal and therefore makes it possible to operate the packaging machine at a high speed.
With the packaging machine described above, the first bottom panel of the bottom forming portion of the container fitted around the mandrel stopped at the station faces to the right, and the third prefolding member is in the form of an arm having a center of pivotal movement to the right of the axis of the same mandrel at a predetermined distance therefrom and extending leftward from the center, the third prefolding member having a downward projection between left and right ends of a lower edge thereof, a folding guide face extending leftward from a base of the projection, and a fortified folding face extending upward from a left end of the folding guide face, the fold forming portion being movable with the first bottom panel by the operation of the second prefolding member to move past the projection of the third prefolding member in the first operative position upon coming into striking contact with the projection and to thereafter move along the folding guide face from a right end thereof to a left end thereof, the distance from the center of pivotal movement of the third prefolding member to the part of the first bottom panel adjacent to the fold forming portion being approximately equal to the radius of pivotal movement of the fortified folding face when the second prefolding member is in an operative position. The fold forming portion can then be bent to lap over the portion of the first bottom panel adjacent to the base part of the fold forming portion.
When the third prefolding member is adapted to be operated by an actuator different from an actuator for operating the first and second prefolding members, the third prefolding member only can be brought out of operation. This renders the packaging machine usable for producing any container regardless of whether the container has the fold forming portion.
Further when the actuator for operating the third prefolding member is a fluid pressure cylinder having a two-step stroke, the third prefolding member can be moved in two steps readily and reliably.